Method of forming hydroformed member with opening

ABSTRACT

A method for manufacturing a hydroforming member includes the step of providing a blank ( 10 ). The blank ( 10 ) is defined by blank wall ( 16 ). The blank ( 10 ) is placed in a die assembly ( 14 ) having a die cavity ( 12 ) defined by a die surface ( 24 ). The blank ( 10 ) is expanded so that the blank wall ( 16 ) is forced against the die surface ( 24 ) to form the hydroformed member. A portion of the blank wall conforms against a wall-thinning element ( 26, 28 ) positioned along the die surface ( 24 ) to form a removable wall section ( 46, 50 ) in a portion of the blank wall ( 24 ). The removable wall section ( 46, 50 ) is then removed from the blank wall ( 16 ) to form an opening in the hydroformed member.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/425,254, filed Nov. 12, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of manufacturing a hydroformedmember. More particularly, the invention relates to a method ofmanufacturing a hydroformed member with an opening.

2. Description of Related Art

Hydroforming is a process in which high pressure fluid is utilized tomove a blank into conformity with a die surface of a die assembly. Inone example, a tubular blank may be expanded to conform with the diesurface to form a tubular hydroformed member. It may sometimes berequired to form a tubular member with one or more openings. Theseopenings may be made during the manufacture of the hydroformed member.For example, laser cutting may be used to form at least one removablewall section along the tubular member. The removable wall section isthen removed to form the opening. Laser cutting is, however, timeconsuming and expensive, both of which increase manufacturing costs.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a method of manufacturing ahydroformed member includes the step of providing a blank that isdefined by a blank wall. The blank is placed in a die assembly having adie cavity defined by a die surface. The blank is expanded so that theblank wall is forced against the die surface in order to form thehydroformed member. A portion of the blank wall conforms against awall-thin ng element positioned along the die surface to form aremovable wall section in a portion of the blank wall. The removablewall section is then removed from the blank wall to form an opening inthe hydroformed member.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a cross-sectional view of a blank positioned in a die assemblyfor use in a method of manufacturing a hydroformed member according tothe invention;

FIG. 2 is an enlarged, cross-sectional view of circle 2 in FIG. 1;

FIG. 3 is an enlarged, cross-sectional view of circle 3 in FIG. 1;

FIG. 4 is a cross-sectional view of the blank showing a blank wallpartially conformed against a die surface of the die assembly;

FIG. 5 is an enlarged, cross-sectional view of circle 5 in FIG. 4;

FIG. 6 is an enlarged, cross-sectional view of circle 6 in FIG. 4;

FIG. 7 is a cross-sectional view of the blank showing the blank wallcompletely conformed against the die surface;

FIG. 8 is an enlarged, cross-sectional view of circle 8 in FIG. 7;

FIG. 9 is an enlarged, cross-sectional view of circle 9 in FIG. 7;

FIG. 10 is a cross-sectional view of a hydroformed member includingfirst and second removable wall sections;

FIG. 11 is an enlarged, cross-sectional view of circle 11 in FIG. 10;

FIG. 12 is an enlarged, cross-sectional view of circle 12 in FIG. 11;

FIG. 13 is a cross-sectional view of the hydroformed member and firstand second punches removing the first and second removable wallsections; and

FIG. 14 is a view of the hydroformed member and one of the punches takenalong line 14-14 in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 through 3, a tubular blank, generally indicated at10, is disposed within a die cavity 12 of a die assembly, generallyindicated at 14. The blank 10 is formed from a metal material, andincludes a blank wall 16.

The die assembly 14 includes upper 18 and lower 20 die halves. The upper18 and lower 20 die halves define the die cavity 12. In addition, theupper 18 and lower 20 die halves move towards and away from each otherto selectively allow access to the die cavity 12. The lower die half 20includes a die opening 22 that opens into the die cavity 12. It should,however, be appreciated that the die opening 22 may be formed in theupper die half 18.

A die surface 24 extends along the upper 18 and lower 20 die halves ofthe die assembly 14, and further defines the die cavity 12. The diesurface 24 includes a pair of wall thinning elements 26, 28. One of thewall thinning elements 26, 28 is a projecting structure 26. Theprojecting structure 26 includes an extension 30 extending inwardly fromthe die surface 24 into the die cavity 12. The other wall thinningelement 26, 28 is a recessed portion 28. The recessed portion 28 extendsout from the die surface 24 away from the die cavity 12.

The projecting structure 26 is mounted within the die opening 22. Morespecifically, the projecting structure 26 includes a base portion 32disposed within the die opening 22. The base portion 32 has a transversecross-section that corresponds to a transverse cross-section of the dieopening 22. Thus, the base portion 32 is sized to fit within the dieopening 22. The base portion 32 includes an upper surface 34 that isflush with the surrounding die surface 24.

The extension 30 extends upwardly from the upper surface 34 of the baseportion 32. The extension 30 is a generally cylindrical structure havinga circular transverse cross-section. The extension 30 includes acircular, planar top surface 36 and an annular wall 38. The top surface36 is generally parallel to and spaced from the die surface 24 and theupper surface 34 of the base portion 32. The annular wall 38 extendsbetween the upper surface 34 and the top surface 36.

The projecting structure 26 is removably secured within the die opening22. As a result, the projecting structure 26 can be replaced with otherprojecting structures of varying size and shape. Alternatively, theprojecting structure 26 may be integrally formed with one of the upper18 and lower 20 die halves.

The recessed portion 28 is spaced apart from the projecting structure 26along the die surface 24. The recessed portion 28 includes a circularbottom surface 40 and a side wall 42 extending upwardly therefrom. Thebottom surface 40 is generally parallel to the die surface 24immediately surrounding the recessed portion 28.

It should be appreciated that although a pair of wall thinning elementsis disclosed, the number of wall thinning elements positioned along thedie surface 24 may vary. It should also be appreciated that although thewall thinning elements 26, 28 have been shown and described as acylindrical projecting structure and a cylindrical recessed portion, theparticular shape of the wall thinning elements 26, 28 may vary.

When the blank 10 is initially placed in the die assembly 14, as isshown in FIGS. 1 through 3, portions of the blank wall 16 are disposedalong the die surface 24. At the same time, other portions of the blankwall 16 extend away from the die surface 24 and into the die cavity 12.A pressurized fluid is introduced into the die assembly 14 to force theentire blank wall 16 towards the die surface 24. The fluid pressure isgradually increased, as is shown in FIGS. 1, 4, and 7, until the blankwall 16 fully conforms to the die surface 24 to form a hydroformedmember, generally shown at 44 in FIG. 7.

The configuration of the blank wall 16 within the die assembly 14 at anintermediate pressure is shown in FIGS. 4 through 6. Referring to FIG.4, the introduction of pressurized fluid expands the blank 10 and forcesthe entire blank wall 16 against the die surface 24. The blank wall 16begins to conform against the projecting structure 26 and the recessedportion 28. At this time, however, the blank wall 16 is not completelyconformed against the wall thinning elements 26, 28. In particular, theblank wall 16 is only partially conformed against the annular wall 38,as is shown in FIG. 5. Additionally, the blank wall 16 is only partiallyconformed against the bottom surface 40 of the recessed portion 28, asis shown in FIG. 6.

Referring to FIGS. 7 through 9, as the hydroforming of the blank 10 iscompleted, the blank wall 16 is fully conformed against the die surface24, the projecting structure 26, and the recessed portion 28. A firstremovable wall section 46 of the blank wall 16 is disposed along the topsurface 36 of the extension 30. The blank wall 16 includes a firstperimeter area 48 surrounding the first removable wall section 46. Thefirst perimeter area 48 has a reduced, cross-sectional thicknessrelative to adjacent portions of the blank wall 16.

Similarly, a second removable wall section 50 of the blank wall 16 isdisposed along the bottom surface 40 of the recessed portion 28. Theblank wall 16 includes a second perimeter area 52 surrounding the secondremovable wall section 50. The second perimeter area 52 has a reduced,cross-sectional thickness relative to adjacent portions of the blankwall 16. Thus, the wall thinning elements 26, 28 cause localizedthinning of the blank wall 16.

As the blank 10 expands outwardly, the blank wall 16 is subjected to ashear force around the edge of the top surface 36 of the extension 30.Similarly, the blank wall 16 is subjected to a shear force around theedge of the die surface 24 surrounding the side wall 42. The shear forcecreates stress fractures 65 in the blank wall 16 at the first 48 andsecond 52 perimeter areas. The stress fractures 65 are helpful duringremoval of the first 46 and second 50 removable wall sections from theblank wall 16.

Referring to FIGS. 10 through 14, upon completion of the hydroformingprocess, the hydroformed member 44 is moved out of the die assembly 14.The first removable wall section 46 projects inwardly from the blankwall 16 while the second removable wall section 50 projects outwardlyfrom the blank wall 16. One or both of the first 46 and second 50removable wall sections, which are generally circular, are removed toform openings 54, 56 in the hydroformed member 44. Removal of at leastone of the first 46 and second 50 removable wall sections is achieved bystriking the removable wall sections 46, 50 with a force sufficient tocompletely separate the removable wall sections 46, 50 from the blankwall 16 in the area of the first 48 and second 52 perimeter areas. Thereduced wall thickness at the first 48 and second 52 perimeter areasfacilitates the removal of the first 46 and second 50 removable wallsections. It should be appreciated that the removable wall sections 46,50 can be formed in a wide range of sizes and shapes in variouslocations along the hydroformed member 44 to form openings of varioussizes and shapes.

In a preferred embodiment, punches 58, 60 are used to remove one or bothof the first 46 and second 50 removable wall sections from the blankwall 16. Each punch 58, 60 is cylindrical and has a striking surface 62that is approximately the same size and shape as the first 46 and second50 removable wall sections. It is however, contemplated that the sizeand/or shape of the striking surface 62 may differ from the first 46 andsecond 50 removable wall sections.

The punches 58, 60 may strike the respective first 46 and second 50removable wall sections a single time or multiple times in order toremove the first 46 and second 50 removable wall sections from the blankwall 16. Referring to FIG. 10, it is appreciated that the punches 58, 60strike from outside of the hydroformed member 44 to remove the first 46and second 50 removable wall sections. At the same time, it is alsoappreciated that the punches 58, 60 may be positioned in the interior ofthe hydroformed member 44 to remove the first 46 and second 50 removablewall sections from within.

Although complete removal of the first 46 and second 50 removable wallsections from the blank wall 16 has been described, it is alsocontemplated to form a hydroformed member in which a thin-walledperimeter area partially surrounds a portion of the blank wall 16 toform a flange or similar outwardly extending structure. For example, awall-thinning element could be included in a die assembly that forms aU-shaped, thin-walled perimeter area around a portion of the blank wall16 so that an angularly extending flange is formed on the hydroformedmember 44 when the thin-walled perimeter area is struck.

In a method of manufacturing a hydroformed member according to theinvention, the blank 10 defining the blank wall 16 is provided. Theblank 10 is placed within the die assembly 14, which includes the diecavity 12 defined by the die surface 24. A pressurized fluid isintroduced into the die cavity 12 to expand the blank 10. As a result,the blank wall 16 is forced against the die surface 24 to form thehydroformed member 44. The blank wall 16 is completely conformed againstthe wall thinning elements 26, 28 along the die surface 24 to form thefirst 46 and second 50 removable wall sections along the blank wall 16.The first 46 and second 50 removable wall sections have respective first48 and second 52 perimeter areas of reduced wall thickness. At the sametime, stress fractures 65 may be created at the first 48 and second 52perimeter areas of the blank wall 16. The hydroformed member 44 is thenmoved out of the die assembly 14. Finally, the first 46 and second 50removable wall sections are removed from the blank wall 16 to form theopenings 56, 58 in the hydroformed member 44. The reduced wall thicknessof the first 48 and second 52 perimeter areas of the blank wall 16facilitates the removal of the first 46 and second 50 removable wallsections. The removal of the first 46 and second 50 removable wallsections is further facilitated by the stress fractures 65.

The invention has been described in an illustrative manner. It is to beunderstood that the terminology, which has been used, is intended to bein the nature of words of description rather than of limitation. Manymodifications and variations of the invention are possible in light ofthe above teachings. Therefore, within the scope of the appended claims,the invention may be practiced other than as specifically described.

1. A method of manufacturing a hydroformed member comprising the stepsof: providing a blank defined by a blank wall; placing the blank in adie assembly having a die cavity defined by a die surface; expanding theblank by introducing pressurized fluid into the die cavity to force theblank wall against the die surface and form the hydroformed member;conforming a portion of the blank wall against a wall-thinning elementpositioned along the die surface to form a removable wall section in aportion of the blank wall; and removing the removable wall section fromthe blank wall to form an opening in the hydroformed member, wherein theremoving step includes striking the removable wall section.
 2. A methodas set forth in claim 1 wherein the removing step includes striking theremovable wall section multiple times.
 3. A method as set forth in claim1 wherein the conforming step includes partially fracturing a portion ofthe blank wall surrounding the removable wall section.
 4. A method ofmanufacturing a hydroformed member comprising the steps of: providing ablank defined by a blank wall; placing the blank in a die assemblyhaving a die cavity defined by a die surface; expanding the blank toforce the blank wall against the die surface and form the hydroformedmember; conforming a portion of the blank wall against a wall-thinningelement positioned along the die surface to form a removable wallsection in a portion of the blank wall; removing the removable wallsection from the blank wall to form an opening in the hydroformedmember; and moving the hydroformed member out of the die assembly priorto the step of removing the removable wall section from the blank wallto form the opening in the hydroformed member.
 5. A method as set forthin claim 4 wherein the expanding step includes introducing pressurizedfluid into the die cavity.
 6. A method as set forth in claim 5 whereinthe removing step includes striking the removable wall section.
 7. Amethod of manufacturing a hydroformed member with an opening using ablank, having a blank wall and a removable wall section, and a dieassembly having a die cavity, a die surface defining the die cavity, andat least one wall-thinning element disposed along a portion of the diesurface, the method comprising the steps of: placing the blank in thedie cavity; expanding the blank by introducing pressurized fluid intothe die cavity to force the blank wall against the die surface;conforming a portion of the blank wall to the wall-thinning element toform the removable wall section; and removing the removable wall sectionfrom the blank wall to form the opening in the hydroformed member,wherein the removing step includes striking the removable wall section.8. A method as set forth in claim 7 wherein the removing step includesstriking the removable wall section multiple times.
 9. A method as setforth in claim 7 including the step of moving the hydroformed member outof the die assembly prior to the step of removing the removable wallsection from the blank wall to form the opening in the hydroformedmember.
 10. A method as set forth in claim 7 wherein the conforming stepincludes partially fracturing a portion of the blank wall surroundingthe removeable wall section.